Fuel tanks in vehicles typically have a high pressure fuel pump within the fuel tank for supplying fuel to an engine of the vehicle. While in use, the engine is generally unable to utilize all the fuel supplied by the high pressure pump. Accordingly, some vehicles have been equipped with a return fuel line to redirect the unused fuel back to the fuel tank for recirculation. The returned fuel generally has been heated, and results in forming vapor bubbles when discharged into the fuel tank. The presence of vapor bubbles in the fuel tank is undesirable, particularly if the vapor bubbles are drawn into the high pressure fuel pump, which can negatively impact the efficiency of the fuel pump and the flow rate of fuel delivered to the engine.
Various attempts have been made to eliminate the opportunity for vapor bubbles to enter the fuel pump. In U.S. Pat. No. 5,728,292 to Hashimoto et al, fuel returning from an engine is directed into a return fuel chamber of a fuel filter. The return fuel chamber is constructed of a meshed filter material, wherein one wall of the return fuel chamber forms a common wall with a main filtration chamber. The return fuel chamber has an upper wall with a check valve allowing fuel vapor to exit through the check valve into the bulk fuel in the fuel tank. The returned fuel within the return fuel chamber is free to flow through the common wall and into the main filtration chamber for entry into the inlet of a high pressure fuel pump. In addition, fuel surrounding the main filtration chamber other than the fuel in the return fuel chamber is free to flow directly into the main filtration chamber and then to the inlet of the high pressure fuel pump. Accordingly, the fuel filter in the '292 patent relies on the common wall between the main filtration chamber and the return fuel chamber to separate fuel vapor from the fuel supply to the high pressure fuel pump, and thus, to the engine.